How to calculate chmod permissions
- Tick read, write, and execute for the owner, the group, and others, or pick a common mode such as 755.
- Or type the octal number (755) or the symbolic form (rwxr-xr-x) and watch the checkboxes follow.
- Enter the file name, then copy the ready-made chmod command.
The tool shows both the numeric command (chmod 755 file) and the symbolic one (chmod u=rwx,g=rx,o=rx file). Add -R to change a folder and everything inside it.
Questions
Is anything sent to a server?
No. The calculator is plain arithmetic that runs in your browser. Nothing you type leaves the page.
What do the three octal digits mean?
The first digit is for the owner, the second for the group, and the third for everyone else. Each digit adds up read (4), write (2), and execute (1). So 7 is read, write, and execute, 5 is read and execute, and 4 is read only.
What is the difference between 755 and 644?
755 (rwxr-xr-x) lets everyone read and run the file but only the owner change it. It suits scripts and folders. 644 (rw-r--r--) lets everyone read it and only the owner change it, and is the usual mode for regular files.
What are setuid, setgid, and the sticky bit?
They are the fourth, leading octal digit. Setuid (4) and setgid (2) run a program with its owner’s or group’s rights. The sticky bit (1) on a folder such as /tmp stops users from deleting each other’s files.
Is 777 safe?
Rarely. It lets any user on the system change or replace the file. Prefer 755 for folders and programs, 644 for files, and 600 for private files such as SSH keys.
Credits
Built by OneTooling using standard browser features. No third-party code runs on your data.